1. Field of the Invention
The present invention relates to washing machines, and more particularly, to a method for fabricating a stator core of an outer rotor type BLDC motor applicable to a direct coupling type drum type washing machine.
2. Discussion of the Related Art
In general, a drum type washing machine washes laundry by using a friction force between a drum rotated by a driving power of a motor and laundry in a state detergent, washing water, and the laundry are introduced into the drum, shows almost no damage to, and entangling of the laundry, and has pounding, and rubbing washing effects.
In the related art drum type washing machines, there are an indirect coupling type in which the driving power is transmitted from the motor to the drum through a belt wound on a motor pulley and a drum pulley indirectly, and a direct coupling type in which a rotor of a BLDC motor is coupled to the drum directly, to transmit the driving power from the motor to the drum, directly.
The type in which the driving power of the motor is transmitted to the drum, not directly, but indirectly through the motor pulley and the drum pulley, has much energy loss in the course of power transmission, and causes much noise in the course of power transmission.
According to this, for solving the problems of the indirect coupling type drum type washing machines, it is the present trend that use of the direct coupling type drum type washing machines with the BLDC motor is increasing.
FIG. 1 illustrates a longitudinal section of a related art drum type washing machine.
Referring to FIG. 1, the related art drum type washing machine is provided with a tub 2 mounted on an inside of a cabinet 1, and a drum 3 rotatably mounted on a central portion of an inside of the tub 2. There is a motor in rear of the tub 2, wherein a stator 6 is secured to a rear wall of the tub, and a rotor 5 surrounds the stator 6, and is connected to the drum 3 with a shaft passed through the tub.
In the meantime, there are a door 21 mounted on a front of the cabinet 1, and a gasket 22 between the door 21 and the tub 2.
There are hanging springs 23 between an inside surface of an upper portion of the cabinet 1, and an upper portion of an outside circumferential surface of the tub 2, and a friction damper 24 between the inside surface of a lower portion of the cabinet 1, and a lower portion of the outside circumferential surface of the tub 2.
FIG. 2 illustrates a perspective exterior view of the stator in FIG. 1, and FIG. 3 illustrates a reference drawing showing the steps of a process for fabricating a related art stator core.
In a related art method for fabricating a divisional core DC type stator core, a sheet of metal plate, which is a base metal BM1, is punched out with a press to form a unit core having Ts 151, a base portion 150, and projected portions 500 on opposite side of the Ts 151 each for forming fastening hole 500a therein, the unit cores are stacked to a required height, to form a unit core assembly, the unit core assemblies are connected to each other in a circumferential direction, and the connected portions are welded, to complete fabrication of the stator core.
The projected portion 500 on the unit core provides a fastening hole 500a for fastening the stator 6 to the rear wall of the tub, and serves to support a fastening force of a bolt.
In the meantime, FIG. 4 illustrates an enlarged view of ‘A’ part in FIG. 1, showing a rotor of plastic with a cylindrical frame, a back yoke 50 on an inside surface of the frame essentially required for providing a magnetic path, and magnets M attached to an inside surface of the back yoke 50.
Alike the core, the back yoke 50 is also fabricated by punching an electric sheet with a press.
However, the related art has the following problems.
The individual processes for fabricating the divisional core DC for fabricating the stator, and the back yoke 50, not only require much working hours, but also result in waste of material.
That is, the fabrication of the divisional core DC and the back yoke 50 by separate fabrication processes increases fabrication steps compared to a case both the divisional core DC and the back yoke 50 are fabricated at a time, and the separate provision and processing of base metal BM1 for the divisional core DC and the base metal BM1 for the back yoke 50 causes to increase wastes of the base metal with much loss of material.
In the meantime, instead of the divisional core DC, though so called cylindrical core which is continuous in a circumferential direction without discontinuity may be applicable, in this case too, the back yoke 50 is still required to process separately, above problem can not be solved.